When materials are crushed or pulverised using interparticle crushing, two opposed rotatably mounted rolls, separated from each other by a gap, form a draw-in nip where the materials are drawn in, either force fed or fed by gravity, and crushed against each other. An advantage of interparticle crushing is that an effective crushing may be achieved, even to very small grain sizes, with a reduced energy consumption as compared to many other crushing techniques. Further, the level of noise during the process is essentially reduced as compared to other crushing techniques.
The present invention relates to an improved wear resistant element for a roll arrangement using interparticle crushing and single particle crushing wherein great wear conditions exist during crushing or pulverising of materials between two rolls in the roller arrangement. The outer surfaces of the roll are subjected to extraordinarily high stressing from which, among other things, high wear emerges. It has been known to counter this wear by means of different shaping and coating of the roll surfaces exposed to the wear.
EP-699 479 discloses rolls of high-pressure roll presses for the compressive size reduction of granular material having hard surfaces with nub pins which are wear-resistant and suitable for autogenous wear protection. The nub pins, which have a long potential service life even under the action of high compressive loads, have a radially inner pin part which is easily welded to the roll surface and a radially outer harder pin part protectively covering the radially inner pin part.
There are problems associated with the above mentioned technique. Due to the enormous amount of stress applied on the rollers, the wear resistant nub pins inserted into the surface regions of the rollers must be able to handle a large amount of pressure without failure. However, even nub pins as describes in EP-699 479 wear down in a pace being unsatisfying. The edges of the nub pins are particularly exposed and have a tendency of breaking prematurely, thereby accelerating the wear pace of the nub pins.